For example, the cited document 1 discloses a heating element unit in which heater wires are arranged between at least two sheets of base cloths that are laid on each other, at least two base cloths are joined by a plurality of jointing wires that are parallel to each other, and the heater wire is arranged so as to pass through between the joining wires.
The cited document 2 discloses a tape heater in which a heating element unit is supported on a heating surface on a belt-like base member having heat resistance and flexibility and the entire part thereof is covered by a covering layer composed of a heat-resistant resin sheet.